Loudoun County winemakers had extra reason to shiver as Monday’s overnight temperatures dipped into the 30s. A late-season frost can wreak havoc on grapevines, and last week’s unusually chilly weather did its share of damage to area vineyards.

Doug Fabbioli, owner of Fabbioli Cellars in Leesburg, estimated that up to 50 percent of his vines showed signs of significant frost burn, despite his use of a frost-protection system that circulates warmer air in the vineyard.

The cold weather was reminiscent of a similarly damaging frost in May 2010.

“I got frosted three years ago, and it was around the exact same time,” Fabbioli said. “But this was a really hard one. A lot of people are feeling the pain.”

Steve Mackey, president of the Loudoun Wineries Association and owner of Notaviva Vineyards near Purcellville, said his varietal grape vines were hit particularly hard.

“We probably lost half of our Sauvignon Blanc, if not more,” he said. A protective spray treatment designed to shield the vines from frost damage helped save many of his other vines, he said.

Not all his fellow growers were as fortunate.

“We’ve heard from quite a few of our colleagues, and to the best of my knowledge, I would say everybody that we’ve talked to lost something,” Mackey said. “The extent of the damage varies from place to place.”

Loudoun, which has branded itself “D.C.’s Wine Country,” has more than 35 wineries, more than any other county in Virginia. That number is expected to rise to more than 40 by the end of the year, county officials said. The vineyards are a powerful tourism draw and account for the majority of about $5 million in annual beverage manufacturing sales, officials said.

But Virginia is also a challenging place to grow wine grapes, and unpredictable weather can have a noticeable effect on the production process. Last week’s frost damage could result in reduced wine production, higher prices and a different variety of blends, winemakers said.

“There’s already been a shortage of grapes for the wineries right now. The wineries are growing so fast, but there isn’t enough fruit to support all of them,” Fabbioli said. “So there will be more dipping into fruit from out-of-state in order to feed the market that we have right now.”

Lower-lying vineyards such as Fabbioli’s were most affected by the frost, said Mitch Russ, chairman of the Loudoun Wine Growers Association. But it’s possible that new vine growth could help compensate for the initial loss, he said.

“There is a chance that a secondary crop could replace some of the damaged vines,” he said. “But it’s still quite devastating.”

One night of cold weather can have a lasting effect on a winery’s products, Mackey said.

“This is anywhere from a one-year to a three-year event, depending on how this will continue to reveal itself as we’re blending our wines,” he said. “When we go to pick in 2013 and all of the fruit that’s normally there is not there, then we have to make what we can with what we have.”

Consumers will see the effects next spring, he said, when this season’s white wines will be produced. The effect on red wines won’t be felt for a year or more, because red wines are aged before they are sold.

As Loudoun’s wine industry continues to expand, and winemakers become more experienced and familiar with the Virginia environment, the unexpected should be expected, Mackey said.

“Late spring frost is not a possibility; it’s an eventuality,” he said. “It’s going to hit you at some point. And so this is just one of those times that tests not only the mettle of the business owner but also the strength of the business plan.”

There’s no doubt that Monday night’s weather dealt a powerful blow to the county’s wineries, Mackey said, but they’ve absorbed such blows before and will again.

“No pity parties,” Mackey said. “This is just part of it.”